Individual languages for lang-alt tags are accessed by suffixing the tag name with a '-', followed by an RFC 3066 language code (eg. "XMP:Title-fr", or "Rights-en-US"). (See http://www.ietf.org/rfc/rfc3066.txt for the RFC 3066 specification.) A lang-alt tag with no language code accesses the "x-default" language, but causes other languages for this tag to be deleted when writing. The "x-default" language code may be specified when writing to preserve other existing languages (eg. "XMP-dc:Description-x-default"). When reading, "x-default" is not specified.